Fig. 1. Experimental linear absorption spectrum of the polycrystalline film of (PEA)₂SnI₄ taken at 25 K (black solid line (a)) and of (PEA)₂PbI₄ (25 K, black solid line (b), reproduced with permission from ref. 39.). Theoretical spectra obtained via DFT+GW+BSE simulations at 0 K for (PEA)₂SnI₄ (a) and (PEA)₂PbI₄ (b).